Optical nanofibers in ion-traps

In this project, we aim to integrate optical nanofibers in ion-traps.

In our group, we demonstrated that atoms and molecules can be efficiently coupled to the intense evanescent light field around optical nanofibers. Such nanofibers are realized from standard optical fibers in a heat-and-pull process, resulting in a waist with a diameter of several 100 nm. Ion traps, on the other hand, are one of the most successful systems for manipulating single particles. Trapped ions can be confined for long durations and by tuning the electric trapping potentials one can adjust their position with a precision of a few nanometers.

Being part of the NOIs project (Nanofiber Optical Interfaces for Ions, Atoms and Molecules) we are planning to profit from the advantageous properties of both systems. In collaboration with the Quantum Optics and Spectroscopy Group of R. Blatt at the University of Innsbruck and at the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences we are setting up an experiment in which an optical nanofiber is integrated in an ion-trap. With this setup we plan to map out the evanescent light field surrounding the nanofiber using a trapped ion as a nanoscopic probe and we also plan to make use of the optical nanofiber in order to efficiently excite the ions and to collect their fluorescence. A long-term perspective is to employ this fiber-ion system in quantum information processing (QIP) to interconvert stationary qubits (e.g. ions) and flying qubits (e.g. photons).

As the ion will have to be placed in close vicinity of the nanofiber surface (~ 100 nm separation), charging effects of the fiber surface have to be minimized. There are several possibilities to tackle this problem such as attaching conducting nanowires to the fiber in order to lead charges away. Other ideas are to coat the fibers with thin layers of gold or of transparent conductive oxides (TCO’s), which are widely used in the field of displays and solar cells. Our first approach however, is to adsorb alkali metals onto the nanofiber surface due to their good vacuum compatibility, well known optical characteristics and ease of use. We seek to find operating conditions where both, the transmission and the conductivity of the fiber-layer system, are satisfactory.